Intellectual disability is often poorly understood because its effects vary greatly among those who have it. Many people with intellectual disability are mildly affected and may not be identified until later during school years. Individuals with intellectual disability may also have physical or emotional problems. People with intellectual disability who have a very low intelligence quotient (IQ) have serious limitations in their ability to function. However, with early intervention and appropriate support, they can also lead satisfying lives. The goal of treating intellectual disability is to help children stay in the family and participate in community life. In most states in the United States, they are guaranteed education and other services.
What Is an Intellectual Disability?Intellectual disability begins in childhood and is characterized by limitations in both intelligence and adaptive skills. The following three criteria must be met for a diagnosis of intellectual disability:
- IQ below 75
- Significant limitations exist in adaptive behaviors, such as self-care, socializing, and communicating
- The disability begins before age 18
What Are the Causes?Any condition that impairs development of the brain before birth, during birth, or during childhood can cause intellectual disability. The main causes can be categorized as follows:
Genetic ConditionsGenetic abnormalities may be inherited from parents or may be caused by environmental factors. There are many genetic diseases are associated with intellectual disability. Examples include:
- Phenylketonuria (PKU)—Children born with this rare genetic disorder cannot metabolize phenylalanine (PHE), which is an amino acid found in food. Without proper treatment, PKU can lead to intellectual disability.
- Down syndrome—In a normal fertilized egg, chromosomes exist in pairs. But, in the case of Down syndrome, there are three of chromosome 21.
- Fragile X syndrome—This is caused by mutations of the FMR1 gene, the leading cause of inherited intellectual disability.
Problems During PregnancyUse of alcohol or drugs by a pregnant mother can cause intellectual disability. Smoking can increase the risk, as well. Other risks during pregnancy include:
- Certain environmental toxins such as lead
- Illnesses of a mother during pregnancy that can be passed on to her infant, such as:
- Prescription medications such as isotretinoin and phenytoin
Problems at BirthPrematurity and low birth weight may sometimes lead to intellectual disability. However, other birth complications and conditions or physical stress in the newborn stage may injure an infant's brain.
Problems After BirthOther conditions that can damage a child's brain and possibly lead to intellectual disability include:
- Severe or untreated seizures
- Accidents, such as a blow to the head or near-drowning
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